Syrian rebel groups have announced they are freezing discussions about joining peace talks sponsored by Russia because of "breaches" in a four-day-old cease-fire by the Syrian government.
Government forces intensified attacks around Damascus and Aleppo on January 2 as they sought to secure the cities' water supplies.
In a statement, the rebel groups said that any territorial advances by the army and Iran-backed militias would end the effort to restart peace talks as well as a fragile cease-fire brokered by Russia and Turkey that went into effect on December 30.
"The regime and its allies have continued firing and committed many and large violations...threatening the lives of hundreds of thousands of people," said the statement signed by about a dozen mainly moderate rebel groups operating under the umbrella of the Free Syrian Army.
Russia and Turkey, which back opposing sides in the war, have been working to organize peace talks in the Kazakh capital of Astana later this month in efforts endorsed over the weekend by the United Nations Security Council.
But the cease-fire they brokered in an effort to pave the way for the peace talks, like previous Syrian cease-fires, has been shaky from the start, with repeated outbreaks of violence in some areas, even as it has largely held in others.
The rebel groups questioned Russia's ability to force the Syrian government and its Iranian allies to abide by the terms of the cease-fire deal.
The rebel statement said the main violations were in an area northwest of Damascus in the rebel-held Wadi Barada valley, which government forces and the Iran-backed Lebanese Hizballah group have been trying to recapture in part because a major spring there provides most of Damascus's water supplies.
The Syrian government says rebels have targeted key water infrastructure, causing leaking fuel to poison water supplies and then cutting it off altogether.
The United Nations says at least 4 million people in Damascus have been without water since December 22.
With reporting by Reuters, dpa, and AFP